1. Technical Field
This disclosure relates to interfaces for transceivers, such as interface architectures for coupling transceivers, transmitters or receivers to power lines.
2. Description of the Related Art
Power line communication (PLC) systems are used in many countries for low voltage power network remote control and remote protection and for remote metering of user energy consumption.
The amount of transferred data for these purposes is limited. Therefore the CENELEC EN 50065-1 “A” band reserved for energy utilities, which corresponds to a frequency range from 5 to 95 kHz, can guarantee an adequate data transfer rate. See, EN 50065-1 “Signalling on low-voltage electrical installations in the frequency range 3 to 148.5 kHz—Part 1: General requirements, frequency bands and electromagnetic disturbances.”; P. A. A. F. Wouters, P. C. J. M. van der Wielen, J. Veen, P. Wagenaars, E. F. Steennis, “Effect of cable load impedance on coupling schemes for MV power line communication,” IEEE Trans. Power Del., vol. 20, no. 2, pp. 638-645, April 2005. Likewise in Northern America and in Japan the same services can be supplied with PLC because the regulation is more permissive and frequencies up to 525 kHz can be used, i.e., up to the AM broadcast threshold. A further reference for PLC systems is the IEEE standard 643-2004. See, IEEE Standards-643TM IEEE Guide for Power Line-Carrier Applications, IEEE Std. 643, Jun. 8, 2005.
In recent years energy suppliers are showing an increasing interest for the use of power line communication also in the medium voltage (MV) network, instead of the wireless or GSM communication systems. These communication methods have weak reliability (particularly in bad weather conditions) and high intrinsic (additional) costs. On the other hand the actual solutions for PLC application in the MV network need a dedicated MV coupler, capacitive or inductive, to be installed near each MV/LV transformer substations.
This solution is technically effective but present MV couplers are not so easy to be installed inside the existing MV switchboard. Moreover, the installation needs an interruption of the electrical power.
A problem for PLC application in the MV network is the design and engineering of the MV coupler for the PLC signal. The coupler must have low impedance for the PLC signal and high impedance for the main frequency voltage. Other problems for PLC application in the MV network are the high voltage level, the behavior of the power transformers and of the power cables at the PLC signal frequency.
In the scientific literature there are few studies about medium voltage power line behavior in the PLC frequency range. See, A. Cataliotti, A. Daidone, G. Tinè, “Power line communications in Medium Voltage system: Characterization of MV cables”, IEEE Transactions on Power Delivery, vol. 23, n. 4, October 2008; A. Cataliotti, A. Daidone, G. Tinè, “A Medium Voltage Cable model for Power Line Communication”, IEEE Transactions on Power Delivery, vol. 24, n. 1, pp. 129-135, January 2009. All the actual commercial solutions use a dedicated coupling network, capacitive or inductive, which has to be installed all over the MV network. See R. Benato, R. Caldon, F. Cesena, “Application of Distribution Line Carrier-based protection to prevent DG islanding: an investigative procedure”, Power Tech Conference Proceedings IEEE, Vol. 3, 23-26 Jun. 2003 Bologna.
In 2008 L. Capetta and C. Tornelli, studied the possibility to use the capacitive divider of a VDS as PLC coupler for the MV power network. See L. Capetta, C. Tornelli: “L'evoluzione del Sistema T&D—Metodiche di comunicazione per il monitoraggio, il controllo e le protezioni delle reti di distribuzione” February 2008 Cesi Ricerca. They compared the performance of a dedicated MV coupler with the performance of a capacitive divider of a VDS according to the prescriptions of the IEC 61243-5. They concluded that the capacitive divider can be used for the reception of the PLC signal but not for the transmission. Moreover, the authors suggest realizing a high impedance receiver but do not explain how to adapt the receiver to the capacitive divider to obtain the higher received signal. Finally the authors concluded that the capacitive divider can not be used for bidirectional communication but only for the network characterization.